Observational constraints on the identification and distribution of chaotic terrain on icy satellites

We outline the observational constraints required to identify chaos regions on Europa. Large incidence angle, rather than high resolution, appears to be the primary observational requirement for identifying chaos. At incidence angles >70°, chaos can be identified on Europa at image resolutions as low as 1.5 km/pixel. Similar images obtained at moderate or low incidence angles (<50°) require image resolutions upwards of ∼250 m/pixel to identify chaos. If global images of Europa can be acquired at high incidence angles, the majority of its chaotic terrain can be identified, helping to constrain models of chaos formation and distribution. Furthermore, our results indicate that the areal coverage of chaos may be more uncertain than previously reported, representing as little as 10% or as much as 50% of the non-polar regions of Europa. These guidelines will aid in the development of optical instruments for future Europa missions, as well as other icy bodies, such as Triton.